An IGBT (Insulated Gate Bipolar Transistor) is a composite power electronic device, which is equivalent to a BJT (Bipolar Junction Transistor) with a thick base region driven by a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The IGBT not only has features of the MOSFET, such as a rapid response, a high input impedance, a great heat stability and a simple driving circuit, but also has features of the BJT, such as a high current density, a low on-state voltage drop and a high withstand voltage and, thus is widely used in power electronic devices.
Common driving circuits for an IGBT (such as EXB841, A316J, M57962) are generally isolated from the IGBT via an optical coupler. As shown in FIG. 1, the driving circuit comprises an MCU (Micro Control Unit) U1, a high speed photoelectric coupler U2, a transistor Q1 and a transistor Q2 for driving an IBGT module U4, a current-limiting resistor R1 for driving the high speed photoelectric coupler U2, a resistor R2 coupled with the transistors Q1 and Q2, a gate driving resistor R5, a resistor R4 for discharging a gate of the IGBT module U4 and preventing static, a voltage stabilization diode ZD1 and a voltage stabilization diode ZD2 used for overvoltage protection. The MCU U1 outputs a driving signal from a pulse-width modulation waveform output terminal PWM_1 to the resistor R1 so as to drive the photoelectric coupler U2 to work. Then, the photoelectric coupler U2 outputs a control signal to drive the transistors Q1 and Q2 to work via the resistor R2, such that the transistors Q1 and Q2 output an IGBT driving signal which drives the IGBT module U4 to work via the resistor R5.
As shown in FIG. 1, the gate driving resistor R5 is fixed in the circuit, and a resistance of the gate driving resistor R5 is constant and cannot be adjusted according to a power of the IGBT module U4, thus impacting operating performance of the IGBT module U4.